text:
Is there any reason not to get a student pilot certificate now?
I hope to get a PPL, IR, and possibly CPL someday. It looks like obtaining a student pilot certificate does not require anything except being 16 or older, knowing English, and completing a free application. Is there any reason not to get an SPC now, so I'll have one less thing to worry about if/when I eventually start flight training?

There is no advantage to doing so. One reason not to the requirement to find a CFI who will do the IACRA paperwork for you. When you are actually in training, a CFI will do this as a matter of course. The process requires meeting in person, so it is likely a CFI will charge you for their time if they are willing to do so at all.
As you mention in a comment, it appears to be an option to file an application form in dead tree format at an FSDO. In that case replace paying a CFI for their time with whatever amount of your own time that takes.
If you anticipate moving any time between now and starting flight training, having the certificate already would also oblige you to notify the FAA of your address change before exercising the certificate. That's one more thing to worry about.
On the other hand, if you have no medical problems, I would recommend you get the medical now. If you are under 40 a third class medical is good for five years, and it will allow you to use Basic Med afterwards, which is not possible without having a previous medical.

According to https://www.faa.gov/pilots/become/student_cert , you can apply directly to an FSDO for free. Is there any reason why that wouldn't work?

@Someone I'm not familiar with that process, but sounds like it should work. I suppose if you live close to your FSDO that's an option. I really, really wouldn't bother if you have anything better to do, though.

If you know you are going to have some medical complication (that you expect to be able to resolve), then you should start the process right away.
For example, let's say you have some minor color vision deficiency.  You need to go for your medical, fail the color vision test, then get a referral to an ophthalmologist who will petition the FAA to grant a practical eye exam.  You will then be able to travel to an FSDO and perform a practical signal light gun test.  If everything goes well, you will be granted a color vision waiver and your student pilot certificate.
Every step of this process involving the FAA takes 90 days.  Add in the time to get the referral and for the doctor to respond -- this process can easily take six to nine months.
You really do not want to interrupt your flight training with a long delay, so if you are going to face something like this, go ahead and start the process immediately.

Thank you! I don't anticipate any medical issues, so I assume none of this applies in my case?

@Someone, no one ever anticipates any medical issues, but unfortunately the MEs often find some anyway :( As someone whose flying career was derailed for decades due to medical issues, I would urge you to get the medical certificate done as soon as possible while you're young and healthy. That will unlock BasicMed for you for the rest of your life, which is a much lower and easier standard to clear than an actual medical certificate.


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How many planes do ATC controllers assist in taking off/landing each day?
I know controllers have several short shifts each day with interval breaks but I was wondering how many planes they assist in taking off/landing depending on what type of controller they are each day? Locational wise perhaps LHR? (London Heathrow)

From the title of your question (taking off / landing planes), I assume you are asking about a tower controller. As you may know, most air traffic don't work in a control tower, but are en-route controllers working in an ACC (area control center).
The number of planes a tower controller handles each day is of course highly dependent on the airport traffic conditions (november, for example, is a quiet month). I work in an European single-runway airport, where the runway capacity is 40 flights / hour (landings and departures included) in optimal conditions. Controllers usually work around 5 effective hours per day, so the theoretical maximum number of planes would be 200 planes. In practice, it is very unlikely that a controller will actually control that number of aircraft, because the runway is used at maximum capacity only during peak hours (early morning, late afternoon and beginning of the evening). Also, a tower controller doesn't only work at the tower position, she will also be typically work a clearance delivery and an approach position.

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How do Air Traffic Controllers determine which planes take off in a certain order?
Does it depend on the weight of an aircraft? If two planes requested take off permission and taxied out to the runway at the same time what would determine which plane takes off first (is it to do with weight or flight path?)
If you have an A320 and an A380, which would take off first?

The busier airports around the world are slot controlled, meaning that each flight is assigned a designated departure or arrival time that they must be ready for. In this case it’s pretty straightforward who goes first - whoever has the first slot.
Non-slot controlled airports are usually on a first come first served basis, with some exceptions. Private flights have to wait for scheduled airline flights, and airliners wait for air ambulances. If two aircraft are departing on the same route, the faster one will go first if they have a significant speed difference. And the heaviest aircraft need greater separation for wake turbulence, so an A320 might get preference over an A380.
That doesn’t mean your A380 will have to wait for 15 A320s though. In practice these are only guidelines and the decision as to who goes first is based on the needs of the traffic system on the whole considering all of the factors at the time.

Can an air ambulance use a slot-controlled airport?  Or do they try to avoid them if they can?

@MichaelSeifert They can and do, but I think more often than not they prefer to avoid them. Just because they have priority that doesn’t mean things happen all that quickly, and smaller airports are often closer to their intended destination.

Based on my experience at not particularly busy Class D and C airports, it is first come, first served with some caveats.
All of the airliners and most of the jets have an IFR flight plan that has a specific time that they have to be off. If they are flying into a busy airport they may also be subject to an EDCT that further restricts when they can take off. The tower will manage traffic so that they can take off in their allotted time frame. In my experience, that mostly means that they will extend the downwind of planes in the pattern to get the big guys off on time. They will also keep you in the runup area a bit longer so that the big guys can take off on time.
I fly out of mostly smaller airports and what is much more common is for the tower to manage the traffic pattern so that airliners and jets can land straight-in or with minimal delay.
The rules might be different at places like Vero Beach where there is a lot of flight training.
To get a feel for how it works at a busy airport, search YouTube for "Kennedy Steve". There are lots of recordings of him moving planes around on the ground at JFK.

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What do Air Traffic Controllers (tower supervisors) say to pilots before takeoff and landing?
I would like to know exactly what Air Traffic Controllers say to pilots pre departure and pre arrival. (In terms of exact information rather than specific example) For example what dialect they use and what info they give.

As the current answer shows this differs somewhat between countries. It can also depend on types of pilot (airliner? GA?) and class of airport. You should edit to include the specifics of what you want to know.

It also depends heavily on if they're flying IFR or VFR.

For the US, the FAA's ATC orders have lots of examples of phraseology for all phases of flight.

Possible duplicate of What ATC entities does a commercial airliner communicate with?

What do you mean by dialect?  ATC phraseology is supposed to be consistent independent of dialect.

ICAO document 4444 contains phraseology and pronounciation in chapter 12. It might however be a little bit difficult (but not impossible) to find online, as ICAO documents are rarely officially published online.
CAP 413: Radiotelephony Manual is published by the Civil Aviation Authority (CAA) in Britain, but is considered reference material for pilot training throughout Europe. CAP 413 is largely built on ICAO doc 4444.
Phraseology in the US differs somewhat from ICAO standard (but is getting more and more harmonized). The Pilot/Controller Glossary published by the FAA may be of some help.


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Why aren't more flight schools covered by the Pell Grant and student loans?
I tried to find flight schools in Alabama that accept the Pell Grant. There are none. The are large collages that do take student loans and Pell but require you to live on campus. So, why are there not more smaller fight schools not set up so I don't have to travel 6 hours away?

A quick trawl through easily accessible documentation online suggests that the Pell Grants are administered through the educational system, up to community colleges and universities. Flight schools are generally commercial training companies, not educational institutions and therefor might not be eligible to participate. I can't be definitive about this, hence not an answer. You might get an answer by reframing the question along the lines of "How is school eligibility for Pell Grants determined?" and posting the question on [academia.se]

It's likely that there's a fair amount of overhead required in order to qualify to receive federal student loans, which smaller organizations probably don't want to deal with. It's also possible that they already have all the business they can handle, so they have no need to attract more by accepting loans.

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What is the optimal jet engine size for maximum range?
I under stand the flying wing has been calculated to have an optimal length. Is their an optimal blade length within a turbine engine for planes as well?

Wouldn't it depend on the size of the aircraft?

It's hard to imagine that engine that will produce the max range for a single seat jet carrying a few thousand pounds of fuel will look very much like the engine that will produce the max range for a jumbo jet, carrying a few hundreds of thousands of pounds of fuel. And a quick visit to an aviation museum, or their website, will indeed confirm the intuition that the engines for the two aircraft do, indeed, look vastly different... with the fan blades of the one as long as or greater than the entire diameter of the other. Good reasons they don't use F-16 engines in the A-380!

Your title question and your description go in rather different directions.
Starting with your title question, check out this paper.
The optimal engine size for maximum range is based on the thrust hook of an engine (Fig 2c in the paper).  The thrust hook is the relationship between TSFC and thrust as you adjust the throttle.
Engines have poor TSFC (relative fuel consumption) at flight idle and lower throttle settings.  They have better TSFC at nearly full power (near the design point for the engine).
Many engines pay a slight fuel economy penalty to get to 100% thrust -- such that their optimal fuel consumption is at about 85% throttle.
A jet's specific range (instantaneous fuel economy) is (Eq 2):
$SR=\frac{V}{TSFC D}$
Typically discussed in nmi/lb of fuel -- think like mpg for a car.
In cruise, $L=W$ must be true, so we'll often think of range in terms of the range parameter (Eq 3):
$RP=\frac{V}{TSFC}\frac{L}{D}$
We've multiplied both sides by $W$ and substituted $L=W$ on the RHS.  The range parameter shows us that for best range of a jet aircraft, we want to maximize $V L/D$ and minimize $TSFC$.
Fun games can be played by multiplying by the speed of sound divided by the speed of sound ($a/a=1$) -- allowing us to write the velocity in terms of Mach number -- replacing $V L/D$ with $M L/D$ which you may have seen around.  In this case, the speed of sound gets absorbed into the assumed altitude variation of TSFC, where $TSFC=TSFC_0 \sqrt{\theta}$ and the speed of sound variation between sea level and altitude provides the $\sqrt{\theta}$.
To maximize range, you want to simultaneously maximize $M L/D$ and minimize $TSFC$.  This requires matching the aircraft (drag polar and wing loading) to the operating condition (speed and altitude) while sizing the engine such that the cruise throttle achieves best TSFC while $T=D$.
If the engine is too big, it will cruise near flight idle and will pay a substantial TSFC penalty.  If the engine is too small, it will cruise at maximum throttle and a small TSFC penalty.  If the engine is smaller than that, it won't be able to reach your desired flight condition (altitude/speed).  This tradeoff is illustrated in Fig. 4 of the paper.
The other answer (that says the engine does not enter into the equation) is based on a handful of simplifications.  Specifically, TSFC being constant with throttle, speed, and altitude (none of which are true) and the drag polar ($C_{D,0}$ and $K$) being constant with speed and altitude (also not true).
Your text question - about optimal blade length - gets a lot messier.
First, the most simple thrust equation for a jet engine is $F_n=\dot{m} \Delta V$.  Where $\dot{m}$ is the mass flow through the engine and $\Delta V$ is the change in velocity of the flow through the engine.
The mass flow $\dot{m}=\rho A V$ is the product of the density, the area, and the velocity.  If you are flying at a given flight condition, the freestream density and velocity ($\rho$ and V) are basically determined.  As a designer, our best tool to change $\dot{m}$ is the engine size -- which we relate as the capture area $A$.
We can also effect thrust by increasing $\Delta V$, but know that a high $\Delta V$ engine will be much less efficient than a low $\Delta V$ engine.  So, for fighters and other high performance aircraft, we design for high $\Delta V$ -- whereas for transport aircraft, we design for low $\Delta V$.
For thrust at best efficiency, you want to accelerate a lot of air (high $\dot{m}$) a little (low $\Delta V$).
So when we think about engine size for a given cycle (i.e. given $\Delta V$), we think about changing the capture area -- and engine thrust is proportional to area.
Once you get into the design of the blades, things get a lot more complex.  You likely need to keep the blade tips from going too fast (high transonic or low supersonic).  In the compressor or fan, you need to get a certain pressure rise out of each rotor/stator pair (a stage).  To get a larger pressure rise, you'll want more turning (determined by blade angles and camber) and more stage solidity (blade area per annulus area).  But you can't work a stage too hard without causing stall.  Because of this, engines are designed with multi-stage compressors that work together to compress the flow as much as is needed.
As you have probably guessed, the length of the blades is mostly set by the area at each engine flow station.  The rest of the blade design gets messy.

For a jetliner the range is maximised when it flies at a specific speed called velocity for best range and which has the following value:
$V_{range}=\sqrt{\frac{2W}{\rho S}\sqrt{\frac{3K}{C_{d_0}}}}$
where $W$ is the airplane's weight, $\rho$ is air's density, $S$ wing surface, and $C_{d_0}$ and $K$ the two usual terms expressing the drag coefficient $C_d=C_{d_0}+KC²_l$.
The relevant drag for best range can also be calculated and it is:
$C_{d_{range}}=\frac{4}{3}C_{d_0}$

What is the optimal jet engine size for maximum range?

As it can be seen, the engine does not enter in this equation in any way, so you simply would choose the smallest jet engine able to push the jetliner at that speed and supply enough thrust to win that drag. Obviously an engine thus selected might not guarantee to meet other requirements like the need to take off or to manoeuvre the aircraft.

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How are thermals mapped in real-time?
Related to "How thermals are found" this question about "Gliding your plane to save fuel" details how to use thermals to save fuel. To use thermals to maximize range, can thermals be mapped in real-time using Doppler or sensors or a data base of some type to fly by?

Here is an example of a nice realtime 3D thermal map: https://www.patternpictures.com/wp-content/uploads/Cumulus-clouds-in-blue-sky-panorama-patternpictures-2909-973x632.jpg

@expeditedescent That is nice but I would like to be able to plan a trip based on thermals. I do not know enough yet to read clouds.

You can't accurately plan a trip based on thermals (gliding wouldn't be much of a sport if you could), as they can form and dissipate more or less randomly within just a few minutes. The best indicator of an active thermal is a developing cumulus cloud

@expeditedescent so is there an instrument to detect up and down drafts ahead of the plane? Just say I'm very conservative when it comes to fuel.

The closest you are likely to get it something like this: https://www.skybrary.aero/index.php/Airborne_Wind_Shear_Warning_Systems But I doubt that is anywhere precise enough to locate thermals

@expeditedescent defiantly a start. Very helpful!

No.  Thermal activity in an area can be predicted in a general way based on atmospheric conditions, but not beyond that. The only way to detect thermals in real time is to stumble into them, and/or locate them by the clouds that form their tops.
In any case, the only conditions for which that sort of thing would work would be on one of those lovely soaring days where steady thermal sources and a moderate wind create "cloud streets" where the cumulus clouds line up for you in rows (the cloud being moisture in the air of thermal condensing at the dew point, creating a handy marker for glider pilots - if the air is dry, the thermals are still there but you have no clouds and you can only find them by trolling).
So it could theoretically work -
If: you had that one day of many where the conditions cooperate and you get decent cloud streets, and
If: the thermals were broad in diameter and,
If: your track just happened to match the direction of the cloud streets, and
If: you cruised just below the cloud bases to make it easy to locate them, and
If: you didn't mind the bumps and surges up and down and didn't have passengers that were prone to airsickness.
In those conditions you could push over and reduce power to maintain speed in the thermals when you feel the upward surge entering it, and then do the opposite when out of the thermal when out of it.  You do this automatically anyway when flying on bumpy days, to hold an altitude, although normally it's random as you stumble in and out of lift.
One problem is, between the clouds on the street, the air is sinking, so the period you are in sink cancels out the period you were in lift, to some degree, limiting the benefit pr maybe negating it.
Another problem is you need to slow the airplane down to do this effectively.
Another problem is you have to get good at identifying when you are in lift and in sink and if you have no soaring experience this can be tough.
Now, I do like to take my own homebuilt PL-2 power plane and soar it on good lift days from time to time, by turning it in a "virtual sailplane" by setting power to give a 200 fpm or so sink rate and fly around just above the stall working the lift (the engine is running at about 35-30% power to do this). I call it "power soaring". But I don't do that when going somewhere although I could try to do it cross country if I wanted and was willing to take an hour to go 40 miles.
If you are really serious about saving fuel, forget about trying to exploit thermal lift except as something to do for fun, and where the right opportunity might happen once in a blue moon, and focus on not being in a hurry to get from A to B.
If you aren't in a hurry, you can cruise your airplane at best range speed and power for the maximum MPG (maybe 40-50%), and you can go places in the early morning when the winds are light and the air is smooth, with your engine barely working, and enjoy the scenery sliding by a little bit slower than normal.  Best time to be in the air.
If you're renting however, and paying on a Hobbes meter, the benefit of the fuel saving is going to the airplane's owner, not in your pocket.


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Barrel Roll Airliner Landing

Can this barrel roll in an airliner be ferformed by a skilled pilot? Is this real?

The video probably isn't real, but look at https://aviation.stackexchange.com/questions/12261/is-it-possible-to-do-a-barrel-roll-in-a-large-aircraft-like-a-b737

Is the video fake? What do you think? Or, if you need to ask the question, do you even think? No, it's utterly fake. VTD with extreme prejudice; please don't post that kind of nonsense.

Yep.  Seems legit.

Is it possible to perform a 1g barrel roll in an airliner? Possibly. If the load on the airframe is kept to one positive g, it should be possible. Bob Hoover might have tried it if given the chance. Boeing lead test pilot Tex Johnson did try it at least once on a demonstration flight.
Is it likely to ever happen (again)? No. No owner/operator would allow it. Then, there is the requirement for an aircraft to be certified to perform aerobatics per 14 CFR Part 23.2005. Which no Virgin Atlantic airliner is. I don’t know of any modern type certificated airliner that is certified for aerobatics.
Is this meme a fake? Yes.

A barrel roll is normally under 2G peak on the initial pull and recovery and at the high speed of an airliner it could be kept under 1.5 with little effort.  In fact after the initial pull you can complete the middle third while ballistic, at 0G.  As well, although they are only stressed for 2.5G in transport category, that's fully loaded. An airliner with no passenger load, just fuel, is likely good for well over 3 Gs.  I know of a CRJ900 that experienced over 3 Gs NEGATIVE in an upset incident, and was undamaged, mainly because the cabin was empty.


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How can a plane be cheaply owned by multiple people?
How can multiple owners save on the cost of a plane that sits 1-4 people. If each nonprofessional person contributes equally in money, how would it contracted up to share all the costs are divided fairly. With at least 1 pilot and 1 A&P mechanic to contribute in labor, how many others could "time-share" on one plane before it too much to be worth it? Is there a method or scheme cost efficient and fair?

what you describe could be called a flying club or shared ownership. These sorts of arrangements are common enough that you should be able to find a template for setting up one which contains the details of how maintenance and overhead are covered and how the club's finances must be recorded and reported.
The cost effectiveness and fairness are determined by how money flows into the partnership and how it flows out. I would suggest you look into the Experimental Airplane Association's documentation on airplane ownership.

@nielsnielsen you should drag the comment right into an answer. I am so new and I want to make sure I do it right and cheaply per person. I will check those out. TKS

"worth it" is something only you can decide, for some the luxury of never being blocked on a schedule makes solo ownership "worth it". Most clubs have an hourly rate based on operational cost, fixed costs, and engine reserves where mechanics/A&P's "buy" time with labor hours. I have seen clubs with 5 members and one plane and clubs with 200 members and 5 planes.

AOPA has a great guide to starting a flying club, and another one on shared ownership. I hope that helps! This is a great question but resources come and go, so I'm not posting this as an answer.

Most flying clubs consist of all pilots.  The fact that you mentioned possibly just one pilot and "non-professional others" as co-owners in the manner you did leads me to believe you are more interested in some sort of aero-limousine arrangement.  Are you a pilot?  If not, would you please clarify your intent?  Because what you are describing sounds more like private carriage, which operates under some different rules...

I've been in a couple of partnership syndicates, including one that owned 3 Cessna 180s on floats, that was set up as a limited liability corporation with 15 equity members as shareholders, and more or less operated like a private flying club.
However, the sweet spot for a single airplane partnership is no more than 2-3 owners. Any more, and the potential interpersonal issues and the fact that you are creating a "flying club" are not worth the minor additional dilution of fixed costs going from 3 owners to 4 or more.
A lot of partnerships go sour, and the problem becomes how to sell an individual share in an airplane that the other partners may want to keep, and who don't want to buy you out.  You have to find a buyer who is willing, and the buyer has to be approved by the other two partners.  That can be tough.
It's best done with a written co-ownership agreement that lays out everything in writing to minimize disputes, such as how and who does maintenance, hourly rate to be charged, booking policy, and various rules. Of course you need to have full in-motion hull insurance to protect everybody's equity. Even a two-partner operation should really be run like a mini flying club to keep it going smoothly.
It's also better for the 3 owners to have the maintenance done by a 3rd party, with the partners just paying out equal shares of cash for whatever comes up.  If one of the partners does significant work on the plane, it can create problems with uncompensated work leading to resentment, plus you get disagreements between the partners on what or how things should be done (this happened to a friend that was in an RV-6 threesome and did all the maint - he was secretly relieved when another partner wrote it off when he flipped it (unhurt) and he was cashed out on the hull insurance).  Better to just give it to a mechanic and share the bill.
It can work quite well, because most owners only fly a few dozen hours a year, not enough to justify bearing all the fixed costs, and splitting ownership 2 or 3 ways has little practical impact on availability, but be careful.  Some friends own 1/5th shares in a pristine Aeronca Champ, and it seems to work ok, and the cost dilution makes it pretty affordable, with each owner only having about 4K in equity, a thousand dollar annual split 5 ways, and a 65 horse engine that only burns 4 GPH.

I would disagree a bit.  Was in a 4-way partnership for years, with not many problems.  Didn't have major problems selling shares - I bought into the existing partnership, and a couple of members sold theirs during my time.  WRT maintenance, it very much depends on the individuals. I wound up doing most of it, but that was because I enjoyed it.

Depends a lot on the local market and the type of a/c when it comes to sale ability of shares.  The interpersonal compatibility of the partners is really key, but you don't really know if that's going to work until you try it. The 15 partner syndicate I was in worked fine, but that was mainly because there was someone who took on the job of running it willingly.

what you describe could be called a flying club or shared ownership. These sorts of arrangements are common enough that you should be able to find a template for setting up one which contains the details of how maintenance and overhead are covered and how the club's finances must be recorded and reported.
The cost effectiveness and fairness are determined by how money flows into the partnership and how it flows out. I would suggest you look into the Experimental Airplane Association's documentation on airplane ownership.


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What is needed to go from a student pilot license to a private pilot license?
I will be 16 in a few weeks and I really want to get flying so I am currently thinking that I should get a Student Pilots license and then get a Private Pilot License next summer when I am 17 but I was wondering what is required to advance from an SPL to a PPL? Is it significantly more economically wise to just wait to get a PPL?

Welcome to aviation.SE! Which country are you in?

You have a bit of a misconception about the way these things work.  Everyone gets a student pilot's license before they get a private pilot's license.  The student license is just a step along the way to the private license.  The requirements for getting a student pilot's license are minimal.  It's the equivalent of a "learner's permit" in the automobile world.  The reason that the requirements for a student pilot's license are minimal is that you will be operating under the supervision of an instructor.  Just having the student license does not authorize you to fly an airplane without an instructor on board.  When you hold a student pilot's license, an instructor has to endorse your license for solo privileges in each make and model of aircraft, and also has to endorse your logbook for solo privileges every ninety days.  An instructor also has to review your planning for every cross-country flight, with exceptions for flights to another airport within 25 miles or repeated flights to another airport within 50 miles.  These and other requirements for solo flight under a student pilot's license are spelled out in FAR 61.87 and 61.93.
Without a student pilot's license, there would be no way to build solo flight time as needed to qualify to take the checkride for a private pilot's license.
This answer is assuming that
1) You live in the USA
2) You haven't already learned to fly, and accumulated flight time, in the military..
Highly related-- essentially the same question in fact-- see all answers--
Am I required to obtain a student license before a sport, recreational, or private one?

If you are in the U.S., Title 14 of the Code of Federal Regulations Part 61.3 requires you to have a Student Pilot Certificate in order to solo an aircraft. You have to solo an aircraft in order to get a Private Pilot Certificate per Part 61.109. There is no economical way of going from no pilot certificate to a private pilot certificate without getting a student pilot certificate first. Also, prior to taking the final (for right now) exam called the checkride, you must fulfill the requirements of Part 61.103.
§61.3 Requirement for certificates, ratings, and authorizations.

(a) Required pilot certificate for operating a civil aircraft of the United States. No person may serve as a required pilot flight crewmember of a civil aircraft of the United States, unless that person:
(1) Has in the person’s physical possession or readily accessible in the aircraft when exercising the privileges of that pilot certificate or authorization—
(i) A pilot certificate issued under this part and in accordance with §61.19;
(ii) A special purpose pilot authorization issued under §61.77;
(iii) A temporary certificate issued under §61.17;
(iv) A document conveying temporary authority to exercise certificate privileges issued by the Airmen Certification Branch under §61.29(e);
(v) When engaged in a flight operation within the United States for a part 119 certificate holder authorized to conduct operations under part 121 or 135 of this chapter, a temporary document provided by that certificate holder under an approved certificate verification plan;
(vi) When engaged in a flight operation within the United States for a fractional ownership program manager authorized to conduct operations under part 91, subpart K, of this chapter, a temporary document provided by that program manager under an approved certificate verification plan; or
(vii) When operating an aircraft within a foreign country, a pilot license issued by that country may be used.
(2) Has a photo identification that is in that person’s physical possession or readily accessible in the aircraft when exercising the privileges of that pilot certificate or authorization. The photo identification must be a:
(i) Driver’s license issued by a State, the District of Columbia, or territory or possession of the United States;
(ii) Government identification card issued by the Federal government, a State, the District of Columbia, or a territory or possession of the United States;
(iii) U.S. Armed Forces’ identification card;
(iv) Official passport;
(v) Credential that authorizes unescorted access to a security identification display area at an airport regulated under 49 CFR part 1542; or
(vi) Other form of identification that the Administrator finds acceptable.

§61.109 Aeronautical experience.

(a) For an airplane single-engine rating. Except as provided in paragraph (k) of this section, a person who applies for a private pilot certificate with an airplane category and single-engine class rating must log at least 40 hours of flight time that includes at least 20 hours of flight training from an authorized instructor and 10 hours of solo flight training in the areas of operation listed in §61.107(b)(1) of this part, and the training must include at least—
(1) 3 hours of cross-country flight training in a single-engine airplane;
(2) Except as provided in §61.110 of this part, 3 hours of night flight training in a single-engine airplane that includes—
(i) One cross-country flight of over 100 nautical miles total distance; and
(ii) 10 takeoffs and 10 landings to a full stop (with each landing involving a flight in the traffic pattern) at an airport.
(3) 3 hours of flight training in a single-engine airplane on the control and maneuvering of an airplane solely by reference to instruments, including straight and level flight, constant airspeed climbs and descents, turns to a heading, recovery from unusual flight attitudes, radio communications, and the use of navigation systems/facilities and radar services appropriate to instrument flight;
(4) 3 hours of flight training with an authorized instructor in a single-engine airplane in preparation for the practical test, which must have been performed within the preceding 2 calendar months from the month of the test; and
(5) 10 hours of solo flight time in a single-engine airplane, consisting of at least—
(i) 5 hours of solo cross-country time;
(ii) One solo cross country flight of 150 nautical miles total distance, with full-stop landings at three points, and one segment of the flight consisting of a straight-line distance of more than 50 nautical miles between the takeoff and landing locations; and
(iii) Three takeoffs and three landings to a full stop (with each landing involving a flight in the traffic pattern) at an airport with an operating control tower.

§61.103 Eligibility requirements: General.

To be eligible for a private pilot certificate, a person must:
(a) Be at least 17 years of age for a rating in other than a glider or balloon.
(b) Be at least 16 years of age for a rating in a glider or balloon.
(c) Be able to read, speak, write, and understand the English language. If the applicant is unable to meet one of these requirements due to medical reasons, then the Administrator may place such operating limitations on that applicant’s pilot certificate as are necessary for the safe operation of the aircraft.
(d) Receive a logbook endorsement from an authorized instructor who:
(1) Conducted the training or reviewed the person’s home study on the aeronautical knowledge areas listed in §61.105(b) of this part that apply to the aircraft rating sought; and
(2) Certified that the person is prepared for the required knowledge test.
(e) Pass the required knowledge test on the aeronautical knowledge areas listed in §61.105(b) of this part.
(f) Receive flight training and a logbook endorsement from an authorized instructor who:
(1) Conducted the training in the areas of operation listed in §61.107(b) of this part that apply to the aircraft rating sought; and
(2) Certified that the person is prepared for the required practical test.
(g) Meet the aeronautical experience requirements of this part that apply to the aircraft rating sought before applying for the practical test.
(h) Pass a practical test on the areas of operation listed in §61.107(b) of this part that apply to the aircraft rating sought.
(i) Comply with the appropriate sections of this part that apply to the aircraft category and class rating sought.
(j) Hold a U.S. student pilot certificate, sport pilot certificate, or recreational pilot certificate.

You can Solo at 16, but need to be 17 to get a license. So, that gives you a year to practice, and study up to pass the Knowledge exam if you plan to start now and get your license at 17.
One of the first steps is to log in here,
https://medxpress.faa.gov/medxpress/login.aspx
and then find an Aviation Medical Examiner so you can get a Class III Medical.
 Your instructor can take thru the process to apply for the Student Pilot license. You can do lessons before that, you need the Student Pilot License to solo tho.
Per Sporty's Academy:
"You will need a Student Pilot Certificate before your first solo; that wondrous time when your instructor has enough confidence in your ability to get out of the airplane and send you off by yourself.  You can obtain the certificate at any time prior to the solo."
Lessons aren't cheap, don't do much before an intro flight. Maybe an EAA.org Young Eagles flight at your local airport to check out flying before jumping headlong into spending money.
You will need 20 hours with an instructor, and 20 hours of solo time, minimum for each, before you can take your check ride with an FAA Examiner for your license when you are 17. (There's also a Sports License, but it has restrictions on it. Plan to spend the few extra hours and get the full PPL).
Many states are letting flight schools start training again this week after the months long COVID19 shutdown (you and your instructor will be side by side), so it's a good time to start flying.
If you're really into it, join your local EAA chapter and look into the Ray Scholarship
https://www.eaa.org/eaa/eaa-chapters/eaa-chapter-resources/chapter-programs-and-activities/ray-aviation-scholarship-fund
and maybe get some help paying for your training.
You can study online with these guys, https://checkride-prep.com/, and get an endorsement to take the Knowledge exam at a test site, same as if you had done ground school locally.https://checkride-prep.com/courses/free-online-private-pilot-ground-school/
I was a college grad before I started flying, and just studied the material at home, asking my flight instructor about stuff I didn't understand.
If you look at Top Tasks here
https://www.faa.gov/regulations_policies/handbooks_manuals/
you could start by reading the top 3 manuals. I'd start with the Airplane Flying Handbook.
It can be kind of dry reading, try not to get bogged down it in. You can always go back and refresh on stuff after you've tried some of what the book goes into with an instructor.
Blue skies friend!

CrossRoads -

Welcome to AviationStackExchange. Please be sure to cite references in your answer. A passing score on the knowledge exam lasts for 24 months. You can take the written for a powered aircraft anytime after your 15th birthday & it will count if you get your PPL on your 17th. The medical certificate and the student certificate are separate carts. You get the Med cert from an AME. You have to have an instructor fill out IACRA for the student cert. You don’t need one to get the other (gliders). You can log hours without a student or Med cert. you just can not fly solo or act as PIC.

In many areas, flight schools have been training this entire time through Covid-19. Aviation is considered an essential business. Some flight schools have opted to curtail training as a company policy during this time. But, plenty are flying. If you are getting instruction under Part 61 instead of 141, you need 40 hours of total time. 20 of which must be dual instruction. 10 of which must be solo which you can do at age 16). 2.5 of which can be substituted in an FAA certificated flight simulator. All these rules change if you are flying gliders (solo at 14, private pilot certificate at 16).

You can start training and log it at any age with any or no medical or pilot certificate. You must meet the minimum requirements to receive a certificate. You can get a glider cert with no medical or drivers license. You can get a Sport Pilot Certificate without a medical, just a drivers license. All dual instruction, solo, & total time acquired in the Sport category count towards the Private Pilot Certificate. Although product endorsement is discouraged here, Kingschools.com  M0A.com the finer points.net rodmachado.com & Sportys are the most used & renowned

"(You cando lessons before that, you just technically can't log them" -- I believe this is not correct-- as another comment has pointed out.  So this answer could be improved.


text:
Why is the horizontal stabilizer forward of the vertical stabilizer on the P-51?
Why is the horizontal stabilizer forward of the vertical stabilizer on a P-51? Are there other airplanes that are like this?

Thank you to everyone who commented. I was thinking the placement was primarily due to maneuverability and spin recovery. But that also brings up the question “Why does it take the P-51 1.25 turns to recover from a spin?”

The primary factor affecting the longitudinal placement of the vertical stabilizer is yaw authority in a spin. From Corke, here is a relevant diagram and description:

As illustrated in Figure 6.10 for a conventional tail, the vertical stabilizer is caught in the wake of the horizontal stabilizer during an uncontrolled spin. This makes the rudder ineffective. The solution for a conventional tail design is to move the horizontal stabilizer either forward or aft of the vertical stabilizer position.

Why did the P-51's designers go with the aft position? It's hard to say given the myriad trade-offs inherent in any aircraft design and without an authoritative source, but as ymb1 points out, yaw authority outside of a spin is likely the answer. The P-51 was designed for maneuverability, so being a relatively small airplane it was beneficial to get as much rudder area and lever arm as possible out of the design.
As far as other aircraft go, it's a matter of how similar you think should qualify. The P-36 and P-40 use a somewhat analogous configuration (and indeed the P-51 was designed with their mission in mind), the A6M (Zero) has an aft tail but without the extended rudder, ymb1 mentions the Cessna 162, a couple of the Zenith airplanes come close, and I'm sure there are more.


text:
Bulkhead (Forward and Rear) positions in civil aircraft
I am looking for general positions of forward and rear bulkheads in the civil aviation aircraft. Like, at what percentage of fuselage length from fuselage nose or any other reference point?
Any reference reading material also would be helpful.

Bulkheads are used to enclose the pressurized part of the airframe, so they are just as far apart as that portion of the fuselage.
In a jetliner the forward bulkhead is normally just behind the weather radar while the backward bulkhead is just before the tailcone.
On this A330 cutaway (source), they are the number 5 and 158 respectively:

Obviously in an airplane like the B-52 only the cabin needs to be pressurised and the bulkheads are positioned accordingly, 4 and 42 in this cutaway (source):

Just a clarification:  While bulkheads can be used for separation of pressurized sections of the fuselage from unpressurized sections, this kind of structural member is not exclusively used for that purpose.

@CarloFelicione: yes right, I've assumed the OP meant "pressure" buckheads ("forward and rear" in the title of the question). Thanks for the corrections

On each aircraft, locations are identified by station or frame numbers to facilitate manufacturing and maintenance tasks. For the fuselage these locations can correspond to circular frames used to reinforce the outer skin. The ends of the pressurized cabin correspond to two particular locations e.g. STA 178/STA 1016 for a Boeing 737 NG and FR1/FR77 for Airbus A320.
There are diagrams online showing the stations number, e.g. for a B737-800:

(Source)
A quick online search will easily provide other diagrams for other aircraft. In spite actual lengths are not shown, it is possible to find the ratio you are searching for.
However aircraft families include models of different cabin lengths, to accommodate different customers needs. For example in the A320 family, the A318 (107 seats) is 31.4 m long while the A321 (180 seats) is 44.5 m long. As the the pressure vessel ends have fixed places (aft of radar antenna and forward of tail cone), the ratio pressure vessel / aircraft length will vary.


text:
What is the lightest powered hang glider?
And how light can it be for foot-launch and climbing on its own power?
I know there are stunningly light paragliders, but they are slow, inefficient, the wings wear out quickly, and they are prone to collapse in turbulent weather, unlike delta-wing gliders.

And how fast, efficient, durable, and turbulence-proof do they need to be before they are acceptable?

My knowledge of PHG may be a few years out of date.  To the best of my knowledge most if not all PHGs are hang gliders combined with aftermarket power units, so the question really breaks down into finding the lightest power unit you can find and then identifying the lightest glider that can safely fly the takeoff weight.

You can build an "e-help", an electric propulsion system weighing about 12kg (example and plans). Using it with a light glider like e.g. Finsterwalder-Charly Funfex (24kg) or Perfex (22kg) will probably yield the lightest, most portable powered hang glider package.
No one's building such electric propulsion systems commercially at the moment, but we're working on improving the situation. If you're interested in building or following along, there's epowered hang gliders fb group.

It seems to me like 12kg is well within reach of current gasoline paramotors that don't carry such a huge range compromise.

If you want range, you can have gas powered hang glider harness too (the Mosquito). It weighs more, but it also includes the harness itself so it's probably only a few kg heavier than the electric setup. Electric engine is much better for getting to altitude for a thermal / ridge soaring flight. Gas engine is better for cruising around on your own power. And of course paragliders will always be the lightest and most compact, but you know their downsides.

You mean something like this?

Here's some info from below the video.
"Prop:
23inch / 12 pitch
Motors:
Using Out-runner model aircraft motors
2,600W
Around 140kV - 160 kV
Around 60A
Batteries:
Two lots of 6s cells connected in series
Speed controller (Speedie):
We go twice the amp rating for reliability and think that is about right. So 120A speedie
The 120A "Yipe" seems to work reliably as an entry level unit.
Speed control is via a modified servo tester wired onto the speedie.
Weight:
1.7kg plus batteries (2x10,000A 6s) 2.7kg = 4.4kg.
gives 10 min at full throttle or hours of fun at low revs/used intermittently."


text:
Is there a proper term to use when you're referring to the total number of people on an aircraft, including both the passengers and crew/pilots?
I've found that often when people quote the number of passengers on an aircraft, they exclude the crew/pilots, which they'll provide separately.
Is there a proper term to use when you're referring to or asking for the total number of people on the aircraft, including both the passengers and crew/pilots?

CAP 419 (the UK CAA radio telephony manual, see the glossary) uses 'POB' which stands for '(total) persons on board'

I would answer xyz POB if asked the question. It's a standard enquiry at some airports after landing, together with aircraft registration

The term "complement" is sometimes used for the total capacity of the craft, as in "it has a full complement of passengers and crew on board."

See https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap5_section_3.html
which deals with emergency reporting:
Table 5-3-11
DM57 (remaining fuel) OF FUEL REMAINING AND (remaining souls) SOULS ON BOARD
Note - N response attribute
Report indicating fuel remaining (time) and number of persons on board.
(remaining fuel) ENDURANCE AND (persons on board) PERSONS ON BOARD
While for VFR and IFR flight plans 'persons' is used:
91.153   VFR flight plan: Information required.
(a) Information required. Unless otherwise authorized by ATC, each person filing a VFR flight plan shall include in it the following information:
     (8) The number of persons in the aircraft, except where that information is otherwise readily available to the FAA.
91.169   IFR flight plan: Information required.
(1) Information required under §91.153 (a) of this part;

Souls on board. Living people on board, cadavers do not count.

Please add a reference to back up this answer.


text:
What is boundary layer tripping?
I came across the term "Boundary layer tripping" but I can't really underastand it. After searching on internet I cannot find any video or an image explaining that concept. Could you please explain what is "Boundary Layer tripping" with some figures/illustrations if possible?
I appreciate your help.

would this answer help to answer your question?

Tripping the boundary layer refers to the action of artificially transitioning a laminar boundary layer into a turbulent one. It can happen intentionally (via turbulator) or unintentionally (via imperfect aero-smoothness, such as rivets, bolts, counter-sinks). At the point of boundary layer tripping, the surface protrusion destabilizes the laminar boundary layer and causes the transition to occur earlier than via natural Tollmien-Schlichting instability.
The following is an example of a turbulator tape. It is attached spanwise along the surface of the wing (facing flat against the surface) at the desired chord-wise location where the laminar-turbulent transition is to take place:

Since turbulent boundary layer has higher skin-friction drag than a laminar one of the same Reynolds number, unintentional boundary layer tripping is undesired. That's why wing surfaces must be made flush and smooth. At the same time, since a turbulent boundary layer is much better at resisting flow separation than a laminar boundary layer, tripping the boundary layer can be used to improve stability & control at high angle of attack at the expense of increased skin-friction drag.

You might want to note that the tape is applied flat to the surface, not standing up on edge like in the photo!  If I hadn't seen it before on gliders I would be mis-led by the photo.  Thanks!

@quietflyer Edited. Thanks.

Your zig-zag tape in the picture is merely destabilizing the boundary layer so it will transition downstream without a big separation bubble. Direct tripping is achieved with a trip wire or with dimple tape. And at high lift coefficient tripping is indeed used to lower drag by avoiding a lengthy separation bubble.

@PeterKämpf Agreed


text:
How do swept back wings delay shock wave
Swept back wings can delay the formation of shock wave and increase the aircraft critical mach number of the aircraft, right? But how

The key is to minimize how fast the air is going over the wing.
Aerodynamics for Naval Aviators has information on this subject in and around page 226. Aerodynamics for Naval Aviators.

The ANA will tell you that there is a spanwise component and a chordwise component of velocity associated with the swept wing, and that the only one that matters for critical Mach number is the chordwise component of flow. That is because the wing has to accelerate air over the top of the wing faster than the plane is flying, and only air going "across" the wing gets sped up. The air going "down the length" of the wing does not.
I do not think this is very intuitive of an explanation, so I would describe it a little differently than the ANA. I would say that swept wings delay the shockwave by appearing longer and thinner than the same wing would be if it was unswept. Air passing down the longitudinal axis of a swept wing will see a wing that is "longer" (meaning longer chord length) and with a lower relative thickness than if it passed "sideways" across the wing in the shortest direction. Please see the colored lines that I added to the ANA figure. The red line is the path air will actually take across the swept wing. The blue line is the path the air would take if the wing was unswept. Notice that they are different length lines. The red line is longer, and therefore the wing appears thinner when taking this path. This will have the effect of reducing the apparent thickness of the wing, and accelerating each parcel of air a bit less than if the wing was straight.
Thin wings with a long chord length do not accelerate air as much as a thick wing with a short chord length. Think of a fighter jet vs a STOL bush plane.
In the business of private aviation we get to see a lot of variation of airplane designs, much more so than in the modern airlines. Let's compare two different ways of raising the critical Mach number. We will look at a swept wing Citation Longitude first.

The longitude has a maximum Mach number of 0.84. It achieves that with a swept wing design that makes the wing appear "thinner" to the air that flows over it. The wing is not all that thin, but the sweep makes it appear thinner to the air flowing over it. Again, thinner wings cause the air to accelerate less during its trip over the top of the wing.
Next up, lets look at a different way of delaying the shockwave. A lear 25.

The Lear 25 is the answer to the natural question of "if sweeping the wings makes them seem thinner, why not make them actually thinner?". The Lear 25 has a maximum Mach number of 0.81. It goes nearly as fast as the Longitude because it really does have very thin wings. Since the wings are actually thin, the air wont accelerate as much over the front 1/3rd of the wing (typical location of both maximum air speed and lift), and therefore will delay the shockwave and allow the plane to fly fast. No sweepback needed because the wings are already thin.
Now let's examine one last thing. If making wings thinner from the start is just as good as sweepback, why would you ever use sweepback to achieve the same thing? Structural reasons and storage reasons.
Structural: the main load-bearing member in the wing is called the "wing spar". It runs the length of the wing and is what carries the fight loads. The thicker it is the stronger it is, but also the heavier it will become. You want a light wing spar if possible. Making the spar taller makes it stronger, but also makes your wing thicker. If you can get away with a wing that is taller, you can make the spar taller, and therefore use less material in the creation of the wing spar, creating an overall stronger and lighter wing.
Storage: The Longitude has a range of 3,500 nautical miles. The Lear 25 has a range of only 1,767 nautical miles. The Lear also must make use of the visible wing tip tanks to store fuel. Having a wing that has good internal volume is advantageous because you can put more fuel in the wings and more fuel means more range.
So sweepback delays the onset of the shockwave by appearing to have a lower thickness ratio than an unwept wing. This causes the air to accelerate less over the top of the wing surface and delays the shockwave. This is often considered better than making a wing actually thinner because making the wing thinner would lead to structural issues fitting an acceptably light wing spar and would reduce the internal volume for fuel storage.

Nice answer. Anyway the comparison Cessna vs. Learjet is definitely unfair since they are two very different aircrafts: mtow, wingspan, aspect ratio, engine's thrust, airfoils,... they are all different. Just the fact that the "old" Learjet uses a NACA 64 airfoil while the new Cessna uses a supercritical airfoil is enough to lower significantly the critical Mach number even without considering the swept wing. Thickness is also not that important to reduce the shock wave's strength rather the pressure distribution on the upper surface of the airfoil.

Also range depends on the engines - the much smaller Lear 25 has wings and engines from the late 1950s with an SFC of 126 g/Nh while the Longitude uses modern Honeywell HTF7700L with an SFC of only 43.2 g/Nh - one third of the gas-guzzling J85s of the Lear.

Just to make my point about the unimportance of the thickness reduction: let's take for example the NACA 64 airfoil of the Learjet 25 and let's see how the critical Mach number changes according to the thickness. Let's consider a $C_l$ of 0.4, midway between mtow and empty weight. As visible, the critical Mach number actually decreases (worsens) for thinner airfoils, basically contradicting your answer.

@sophit, this is a question on its own! looking at a lift coefficient of cl=0.4 is not completely fair as all airfoils have a design lift coefficient of cl=0.1 and they should be compared at that point. For the design lift coefficient of cl=0.1, the thinnest airfoil has the highest critical mach number.

@ROIMaison: $C_L=0.4$ is midway between mtow and empty weight, I don't know if 0.1 is ever reached actually

@sophit, then the graph of your source does not have a bearing on the situation at hand.
It's very likely that if they used a NACA64 series, they would have taken the NACA64 4 series, designed for CL=0.4. The critical mach graphs will have the same relationship with thickness (i.e. thinner has a higher M_cr), but then with the peak M_cr at CL=0.4.
It's a well-established phenomenon that all things equal thicker airfoils have a lower M_cr (as there is flow accelerates more due to the thickness)

@ROIMaison: understood and agreed. I just wanted to point out that the equation "thinner = higher critical Mach number" is not always true . But in my opinion this kind of "popular explanation" is anyway not that consistent: if we know that air simply flows straight on the wing, why shall we design the wing like if it were perpendicular to the leading edge instead? We just choose the airfoil taking into account a straight streamline and that's all.

@sophit you're right, there is absolutely more to it, but it's a good example of an engineering model, allowing for quick estimations.

If you are unsure why air will accelerate when flowing over a wing, read this answer first.
Now keep in mind that local curvature will determine the amount of acceleration. In a straight wing that acceleration is in the direction of the original flow speed because the wing surface curvature is highest along chord lines while zero in spanwise direction.
Now sweep the wing. This will also sweep the direction of highest curvature, and with it the direction into which the flow is accelerated. The speed component of the air in the direction of highest curvature is the flow speed times the cosine of the sweep angle. This is the chordwise speed component in EquipmentOperator's answer. Since the acceleration is also a function of flow speed, the acceleration will not only start from a lower level, but is also reduced by the cosine of the sweep angle, leaving more margin before the speed of sound is reached.
With 60° of sweep the cosine of the sweep angle will drop to 0.5, doubling the flight Mach number at which the same acceleration is reached in a straight wing at Mach 1.0, which nicely confirms the graphics in the first picture of EquipmentOperator's answer.
As much as I support his answer, once you know that curvature is key to the understanding of lift, the explanation with the chordwise speed component becomes very intuitive. The apparent reduction in thickness actually has very little to do with the way sweep works. Also, air passing over a swept wing will actually first move towards the wing tip in the region just ahead of the stagnation line, then curve inwards when acceleration kicks in over the forward chord and finally return into its original direction when pressure rises again over the rear wing.

If I were you I'd have elaborated an answer based on this very nice answer of your

@sophit I see we think along the same lines :-)
However, reading this old answer again makes me think I should improve the drawing. It does not show correctly what happens ahead of the wing.

What's actually the source of the first picture in that answer? I can't find anything similar

@sophit Did it myself, using Inkscape.

It increases the effective chord, the effective chord line being parallel to the longitudinal axis, whereas the true chord is perpendicular to the spar axis.
It sort of tricks the air into thinking a wing with, say, a 12% thickness, is an 11% thickness, and the pressure gradients are more gentle and shockwave formation is delayed a bit.
In other words, a swept wing, compared to a straight one with the same area, acts like a wing that is thinner, as far as shockwave formation is concerned.

Also for this answer this comment of mine applies.

My point is that the two airfoil sections have the same thickness, but it's that the thickness ratio and therefore pressure gradient is reduced along the longitudinal axis by sweeping, because the airfoil is effectively "stretched", while the actual thickness, and the overall wing area, is unchanged.  Is that the wrong way to think about it?

"My point is that the thickness ratio and therefore pressure gradient is reduced" understood but a smaller thickness ratio might actually worsen the critical Mach number just like the airfoils in my link where a thinner airfoil has a smaller (i.e. worse) critical Mach number

The benefits of a swept wing have already been known at least since 1935 when A. Busemann presented a paper at the Fifth Volta Conference in Rome about the advantages of a swept wing at supersonic speed (Busemann, A. - "Aerodynamicher Auftrieb bei Überschall Geschwindigkeiten" Luftfahrtforschung, Bd 12, Nr 6, October 3, 1935, pp. 210-220).
Apparently nobody among the attendees (of several nationalities) was able to appreciate that discovery, except the German government that classified that paper the next year. In the following years, further theoretical and practical research was carried out in Germany that verified the property of wing sweep in delaying the onset of the compressibility drag associated with the formation of shock waves.
The same research was independently conducted in the USA (although with some ten years of delay) and have resulted in the seminal paper "Wing plan forms for high-speed flight" by Robert T. Jones.

The answer to this question is anyway of disarming simplicity and it is based on exactly the same principle by which, from an aerodynamic point of view, a fixed airplane invested by moving air in a wind tunnel is perfectly equivalent to the same airplane flying in free air: Galilean transformation.
By virtue of this same principle, the airflow $V_0$ investing a swept wing can be decomposed into:

a 2D airflow perpendicular to the leading edge with speed $V_0cos\Lambda$; and
a spanwise airflow with speed $V_0sin\Lambda$.

(source)
Flowing spanwise from the tip to the root of the wing, the airflow in 2. sees a boring, never-changing aerodynamic body that basically resembles a flat plate at zero AoA. Therefore, this airflow generates no aerodynamic forces (except in the boundary layer but we are so far only interested in what happens in the inviscid flow outside it).
On the contrary, the 2D airflow of 1. sees an airfoil travelling at the speed $V_0cos\Lambda$ which is obviously smaller than $V_0$ of a factor $cos\Lambda$.
So, sweeping the wing we simply cheat a bit making the aerodynamic part of our wing see a smaller speed than the flight one. That's all!

In his paper, Robert T. Jones considers a straight wing invested by a flow with a sideslip$\beta$. Albeit not directly considering a swept wing, this approach is anyway formally equivalent to a swept wing with angle $\beta$ invested by a straight airflow; but it simplifies the theoretical treatment.

In particular, it is proved that "the flow patterns are similar to those occurring in an incompressible fluid except for an increase of the pressures in the ratio
$\frac{1}{\sqrt{1-(\frac{Vcos\beta}{c})²}}$"
The net outcome of this result is that the only component of the speed contributing to the aerodynamic forces is the one perpendicular to the leading edge ($Vcos\beta$) while the component parallel to the wing gives a negligible contribution to them.
Later in the paper it is demonstrated that the same conclusions are valid also at supersonic speeds if $\beta$ is bigger than the Mach cone: in that case the aerodynamic forces depend again only on the (subsonic) speed perpendicular to the leading edge of the wing.

The person's name actually is Adolf Busemann. No need for an umlaut here.

@PeterKämpf: corrected, thanks


text:
Is more lift needed for a stabilized climb

First, the photo depicts a vector diagram during a climb. L means Lift. Lv means the vertical component of lift. Lh means the horizontal component of lift. T means Thrust. D means drag. W means weight. Wh means the horizontal component of weight. Wv means the vertical component of weight. Lh perpendicular to Lv and Wv is perpendicular to Wh.
I have several questions about this.

did I draw correctly?

in a stabilized climb, is T=D+Wh and Lv=W?

if the answer to the above question is "no", then why not. If it is "yes", then in a stabilized climb, L must be greater than when it is in straight-and-level flight(ie greater than W), so that Lv equals to W. Am I right?

what about Lh. What is its role? Does is contribute to drag as well?

Lv=W in any stabilized situation, and in climb L is greater than when level, since L is now more slanted. Lh has no specific role, It just happens to be horizontal, but is not useful for calculations. It does contribute to drag if you wish, but as drag is measured in motion direction, it must be first broken down into components parallel to L and D. Remember there is a single force in this story (the total aerodynamic force), anything else is a (virtual) break down of this force in particular directions useful for some calculation.

@mins -- re "and in climb L is greater than when level" -- I don't agree.  See https://aviation.stackexchange.com/questions/40921/does-lift-equal-weight-in-a-climb/56476#56476 .  Re "Lv=W in any stabilized situation"  -- again I don't agree.  Linked answer shows L < W in steady-state climb, so Lv will also be <W.

@quietflyer: Nice answer. Yes I see you're right, though it's a strange conclusion. However the aircraft now climbs not only on lift, but also on thrust, and with a very powerful engine it could climb on thrust only like a missile or a rocket. So yes (Hitomhi) please disregard my first comment.

@Hitomhi the right angle is next to L, Lv is the hypotenuse.  Note sine climb angle ${\theta}$ x T = is the vertical thrust component.


text:
Is more rudder pressure needed in gliding turns than normal turns
The FAA Airplane Flying Handbook says

the rudder compensates for yawing tendencies when rolling in or out of a gliding turn; however, the required rudder pedal pressures are reduced as a result of the reduced forces acting on the control surfaces

Forces acting on the control surfaces are reduced. Doesn't it need more rudder pressure (so a greater rudder deflection) to generate more force to counteract the reduced force acting on the control surfaces?
Also one more question: reduced forces acting on the control surfaces mean the glide speed is rather slow (since slower speed means reduce forces acting on control surfaces), right?

I think what they mean is less forces acting on the ailerons, therefore, you don't need as much rudder to counteract yaw (since the roll is less)

But if you do want to turn, you do want to achieve the same roll (as in normal fligh), don't you? Then you need to deflect ailerons more. Then the effect of adverse yaw will be greater. Then greater rudder deflection is needed. Am I right?

Not seeing the passage in the Airplane Flying Handbook in context, it's a bit hard to know exactly what the FAA meant.  More to the point, could you be more clear about what you want to know?  You say "Doesn't it need more rudder pressure (so a greater rudder deflection) to generate more force to counteract the reduced force acting on the control surfaces?"-- do you mean compared to a non-gliding (constant-altitude?) turn at the same airspeed?  Or compared to a turn at your normal cruise speed?  If the latter, what is the airspeed in the gliding turn, i.e. what's the delta involved?

Don't overthink this one.  Power differences affect yawing moments and change rudder input requirements. Torque and P-Factor generally mean more right rudder is required with more power than with less, with the engine turning clockwise out front.
But for your purposes, you are only concerned with keeping the skid ball centered, and knowing those effects is just something you keep in mind to anticipate what to do with your feet.
And that basically comes down to:

Applying left aileron, learn to squeeze a bit of left rudder instinctively, then check the skid ball and adjust, "stepping on the ball" with whatever foot is required to keep it centered.  Vise versa for right aileron.
Adding power, learn to squeeze a bit of right rudder instinctively, then adjust, "stepping on the ball" with whatever foot is required to keep it centered.

In the end, you just do whatever it takes with your feet to try to keep the skid ball centered at all times.

I was once an admiral, but only fleetingly. One of my captains only stayed at the back of his ship, he was so stern. Another decorated the front of his with bow-ties. The ship of the third somehow shrunk to his size and cap-sized. Eventually they a-mast some followers and threw me overboard - a rudder upsetting experience...

Are you trying to pun-ish me?  HAR HAR HAR.

Your question may betray a fundamental, (but common) misconception. The rudder is not needed to compensate for yawing tendencies due to turns. It s needed to compensate for yaw due to the displacement of the ailerons needed to roll the aircraft when establishing, (or rolling out of), the bank angle needed for the turn. So as far as the need for rudder, it doesn't much matter what is going on in the turn. What matters is how much aileron you use, (how slow or how fast you roll into the bank)


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Do some right-handed pilots fail to use the left stick of an Airbus?
After years of flying left-hand throttle and right-hand yoke (in the right seat), are there ever first officers who simply cannot transition to the opposite due to particular hand-dominance?
As a corollary, are there any pilots who simply cannot acquire the left-hand dexterity/sensitivity to use the Airbus joystick when transitioning to captain?
And in all cases, are there ever trainees who cannot get used to yoking or throttling with a non-dominant?

If a pilot is still a natural entity, then pilots as a group will have a distribution, between sometime who almost can not graduate from flight school to someone who flies damaged planes to safety, there are ones in the middle, if that's what you are asking.

I'm sure...i'm just asking if anyone has personally experienced this, and what happened...

It would be unthinkable for this to happen, simply because in order for a pilot to get to the point of flying right seat in a commercial environment, they had to fly a LOT of left-seat time, quite a few of those being as CFI's or single-pilot operations. You can't get an ATP without having significant left seat time. As for handedness, I'm right handed, but my left hand is always the one operating the yoke (right does throttle/prop/radios).

Part a pilot's career is transitioning between the left and right seats (single pilot, captain, first officer, flight instructor, etc). By the time a pilot gets to fly airliners they are accustomed to flying in both seats.

To be honest, it takes all of about 10 minutes to transition between a control yoke and a stick.  The more strained process is learning the systems, performance numbers and procedures.  Most certified aircraft have docile handling characteristics and good handling qualities and the kinesthetics feel of the stick quickly becomes accustomed to during the transition process. The more varied and different types of aircraft a pilot has flown, the easier this process is.  Another factor is that many professional pilots are also certified flight instructors and have developed a familiarity with transitioning into new aircraft from both the left and the right seat.
Now some people who learned how to fly one type of plane only and have a lot of hours in it, then attempt to switch to another have problems doing so, mainly due to handling qualities between the two aircraft.  I once saw a guy who recently bought a SR-22 after logging 800 or so hours in a PA-28R Arrow IV.  He seemingly could not land the new Cirrus no matter how hard he tried.  Again with limited flight time in different types and develop habits around the handling of one platform, it becomes harder and harder to change between types regardless of whether they use yokes, sticks, ram’s horns, etc.


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Is less right rudder pressure needed for right chandelles
It is said on the Internet and the FAA Airplane Flying handbook that when rolling out from a right chandelle, the yawing moment is to the right, which partially cancelled some of the left turning tendency's effect. So less right rudder pressure is needed.
However, I don't understand the above. When you turn to the right, the adverse yaw is to the left, right? Then this left yawing moment contribute more to the original left turning tendency, resulting in more left yawing moment. Then, more rudder pressure is needed in such a right chandelle?

No. It is to the left. When performing a chandelle to the right, at the end, the left wing is on the outside of the turn during the rollout, and is therefore moving faster than the right wing, and to roll to the left (rolling out of the right bank), you put the right aileron down, and the left aileron up so the adverse yaw is to the right. Both effects cause a right roll.

It may be more correct to say less left rudder pressure is needed when rolling out (from a right hand turn).  But if one is "finishing near stall speed", staying coordinated would be most important.

No. It is to the left. You may be confused due to thinking that adverse yaw is the result of the direction of the bank,  (or turn), not the roll.. in a right chandelle, at the end, when rolling out to level flight you are rolling to the left, not to the right.
And this will cause adverse yaw opposite the direction of the roll, regardless of the bank angle itself. This is because the aileron deflected downwards, into the airstream on the bottom of the wing, experiences significantly higher drag than the aileron that is deflected upwards.
Also, when performing a chandelle to the right, at the end, the left wing is on the outside of the turn during the rollout, and is therefore moving faster than the right wing, and. as mentioned above, to roll to the left (rolling out of the right bank), you put the right aileron down, and the left aileron up so the adverse yaw is to the right. Both effects cause a right roll.

Understand. Thanks

In many aircraft, the direction and rate of roll is far and away the dominating factor in determining the aircraft's "adverse" or "proverse" yawing tendencies.  The nose typically tends to yaw toward the rising wingtip (in relation to the actual direction of the flight path at any instant.)1
Typically there are also smaller factors whose effects can be noticed while turning with a constant bank angle, which tend to yaw the nose slightly toward the outside of the turn (in relation to the actual direction of the flight path at any instant.)
Which way are we rolling when exiting a right chandelle?  To the left.  It's only because the roll rate is fairly low that any right rudder (to overcome P-factor) is needed at all; with a higher roll rate you'd need to apply left rudder to keep the ball centered.
Footnotes:

Note that when we start to enter a turn from wings-level flight, since our flight path is initially linear, the aircraft's tendency to yaw toward the rising wingtip in relation to the actual direction of the flight path at any instant will also produce a visible "wrong-way" swing of the nose in relation to a distant landmark ahead of the airplane.  This is generally not the case when we are rolling out of a turn, unless the turn rate is rather low and we are using a rather strong roll input, which is an unusual combination.

(not much different than the other existing answer, just a slightly slightly different spin on things)


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What's the difference between these two VOR cones in Jeppesen Approach Charts' profile view?

Both are ILS approaches. In Jeppesen introduction there's a similar icon which is explained as "A "broken" navaid or fix symbol indicates that it does not fall directly in line with final approach track." but both the symbol and the explanation don't match some of the navaid symbols I see.

@RTO LTBY Hasan Polatkan with the cut cone and LTBZ Zafer with the full cone


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Decreasing Area of Axial Compressor
in axial compressor, why the area is decreasing until it reaches the combustor?
and if the answer because of the pressure is inversely proportional to the volume. that's happened when the temperature is constant, and the temperature in not constant in axial compressor!
and if the answer because of Bernoulli statement, the area going decreasing and then the velocity will increase and the pressure will decrease!

Without entering into the details about how an axial compressor works, let's consider the following plot about how the characteristics of the airflow change in a typical turbojet engine:

We see that in the axial compressor:

pressure steadily increases from some 15 to 140 psia (i.e. from 10⁶ to 10⁷ Pa);
temperature rises from some 20 to 300 °C (i.e. 290 to 570 K);
velocity slightly decreases but we just consider it constant for simplicity.

Considering the simple ideal gas law (which retains its validity here) we calculate the density change between the beginning and the end of the compressor:
$P=\rho RT \Rightarrow \rho=\frac{P}{RT} \Rightarrow \frac{\rho_{end}}{\rho_{begin}}=\frac{P_{end}T_{begin}}{P_{begin}T_{end}} = \frac{10⁷ \times 290}{10⁶ \times 570} = 5$
That means that the air has decreased its volume by a factor 5: the section of the compressor must simply keep up with this reduction.
The following is a schematic (source this NASA report) of a J57-P-1 turbojet engine which, by a technological point of view, resembles the previous engine:

As visible in the table, the section area changes from 952 (section 3) to 5800 ft² i.e. of a factor 6, very close to our calculation. Actually if we scale this value taking into account the different
pressure ratio of the two engines (11.5 for the J57 and 9.5 for the turbojet in the first picture) we get a practically equal density change $6 \times \frac{9.5}{11.5}=5$.


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How does increasing the angle of attack increase the lift?
When the pitch of a plane increases (facing upwards), it has a positive angle of attack, and when it decreases to face downwards, it has a negative angle of attack.
Increasing the angle of attack would increase the lift coefficient as a result and vice versa. If all other factors remain the same, then the force of lift would increase as a result.
What I don't understand is that when the pitch is increased, wouldn't the direction of the lift be facing backward, which would push the plane backward?

When the pitch is decreased, the relative direction of lift would face forward. Won't this not only propel the plane forward but also increase the force of lift for the plane?
For planes with a very low thrust-to-weight ratio, won't this effect be magnified? Is there some component of force I forgot to consider?

“What I don't understand is that when the pitch is increased, wouldn't the direction of the lift be facing backward, which would push the plane backward?” Yeah, your hunch is correct, we just call this effect “induced drag” instead of backwards lift.

@MichaelHall -- So induced drag is zero if AoA is negative?  (For a cambered airfoil, it is possible to sustain upright flight at slight negative AoA.)

@quietflyer, no.  If the wing is producing lift it is producing induced drag.  We both know that, so not sure of your point?

@planes: please wait at least 24 hours before choosing an answer in order to give all the people around the world the possibility to come up with an answer

BTW, the square/diamond shapes don’t help your question.  Why not draw actual airfoil shapes?

When the pitch of a plane increases (facing upwards), it has a
positive angle of attack, and when it decreases to face downwards, it
has a negative angle of attack.

Well, sort of.  Strictly speaking, that sentence is only completely true if the flight path is exactly horizontal, and the wing incidence is zero.  But a negative-angle-of-attack generally isn't compatible with sustained horizontal flight.  Read on for more.
You do understand that pitch attitude and angle-of-attack can be two very different things, right?  Pitch attitude is the angle between the longitudinal axis of the aircraft and the horizon, and angle-of-attack is the angle between the wing chord line-- or in some uses, the longitudinal axis of the aircraft-- and the direction of the flight path.  Even if wing "incidence"-- the angle between the wing chord line and the longitudinal axis of the aircraft-- is zero, angle-of-attack will often be very different from pitch attitude.  If you are under the impression that any time we see an aircraft in a nose-down pitch attitude, the wing must be at a negative angle-of-attack, then you need to do some re-thinking. Again read on for more.
Your sentence would be better changed to something along the lines of-- "If the direction of the flight path stays constant, then an increase in pitch attitude corresponds to an increase in angle-of-attack, and a decrease in pitch attitude corresponds to a decrease in angle-of-attack."

What I don't understand is that when the pitch is increased, wouldn't
the direction of the lift be facing backward, which would push the
plane backward?

You need to understand that the Lift and Drag vectors are defined orthogonal (perpendicular) to, and parallel to, the direction of the flight path, respectively.
Not the wing surface (or "chord line").
The flight path is also the direction of the (free-stream) airflow, which we call the "relative wind" -- this is the wind or airflow that the airplane "feels" in flight, regardless of the direction that the external, meteorological wind is blowing-- and that's why the vectors are defined that way.
Take a look at this related answer: Can we show through simple geometry rather than formulae or graphs that the best glide ratio occurs at the maximum ratio of Lift to Drag?.  Note that the Lift vector is not tilted backwards because the aircraft is drawn nose-high, rather it is tilted forwards because the flight path is descending. If the flight path were horizontal and the wings were not banked, and the wings were at a positive-lift angle-of-attack, the Lift vector would point straight up, regardless of the pitch attitude of the aircraft.
Of course, the angle-of-attack can be decreased to the point where Lift is zero, or negative.  In the latter case, if the aircraft is initially upright and the flight path is initially horizontal, the Lift vector will initially point straight down.1 Obviously, that is not compatible with continued horizontal flight-- the flight path will immediately begin to curve (bend) earthwards (downwards), and the orientation (pitch attitude) of the aircraft will immediately start changing as well!
So you can see that in these kinds of discussions, in any specific case we have to understand whether we're taking it as a given that the flight path is continuing on with no change in direction or speed, or not.  If so, all the force vectors must sum to zero (meaning that the force vectors can be arranged into a closed polygon); if not, that constraint is removed.
Here's a more complicated answer that shows the same principal: Does lift equal weight in a climb?.  Note that in none of the vector diagrams is the pitch attitude of the aircraft specified.  And neither is the angle-of-attack of the wing.  But the direction of the flight path (i.e. the climb angle) is.  That's all the information we need to draw the Lift and Drag vectors in their correct orientation.2
Footnotes:

Compare and contrast to the figure labelled "Negative AoA" in the original question.  Generally speaking, this figure has two errors-- one, the direction of the Lift vector is shown as perpendicular to the wing chord line, not the airflow, and two, the Lift vector is pointing generally upward, not generally downward.  To speak more precisely, for a cambered (non-symmetrical) airfoil it is possible for the angle-of-attack to be very slightly negative (just a few degrees) and for the Lift vector still to be in the "positive" direction.  But not at the large negative angle shown in the figure--assuming that the figure is intended to represent horizontal flight, and thus a horizontal airflow.  If the figure is not intended to make any representations about the direction of flight/airflow at all, then we have deeper problems-- this would suggest that the OP is imagining that "Angle of Attack" is synonymous with "pitch attitude".

There was one simplification made in that answer-- the Thrust vector was assumed to be parallel to the Drag vector, and therefore parallel to the flight path.  In reality, the Thrust vector is not defined to be parallel to the flight path, so for any given direction of the flight path, the pitch attitude of the aircraft does affect the direction of the Thrust vector.  But not the direction of the Lift and Drag vectors.

Both in this question and the previous, the OP seems to be focused on the idea that the Lift vector may somehow propel the aircraft forwards, or slow the plane down. The short answer is "it doesn't, because the Lift vector contains no component parallel to the flight path". At least as viewed from the airmass reference frame. For a bit of a mind-teaser from a different reference frame, see https://aviation.stackexchange.com/a/75480/34686

when the pitch is increased, wouldn't the direction of the lift be facing backward, which would push the plane backward?

No.
By definition lift is the part of the aerodynamic force perpendicular to the airflow, not to the body.
The following picture (source) is more correct:

Lift ($C_l$) is always perpendicular to the "Flow direction" and drag ($C_d$) is always parallel. The angle of attack $\alpha$ makes the intensity of lift and drag change but not their direction.
In general a higher (positive) AoA increases both lift and drag, lift in a more or less linear way (in blue in the following plot), drag (in red) in a quadratic way:

Lift is defined to be perpendicular to velocity.  Drag is always parallel to velocity.
If the aircraft is moving 'horizontal', then lift always points 'up' and drag always points 'back'.
We call the Lift / Drag axis system 'Wind Axes' because they are aligned with the freestream velocity (the wind).
We also often use 'Body Axes' because they are attached to the aircraft's frame of reference (the body).  If you take a paintbrush and paint an axis system on the aircraft, those could be body axes.  We usually call these Axial (from nose to tail) and Normal (out the top of the aircraft).
The angle of attack is (by definition) the angle between the Body axis in the axial direction and the Velocity.  I.e. the angle of attack provides the transformation from Body to Wind axes.
When angle of attack is zero, they are the same.  So, 'Axial' and 'Drag' are aligned and 'Lift' and 'Normal' are aligned.
Your intuition on lift/drag probably starts here -- but is more properly attacked to Normal/Axial force components.
When angle of attack increases, the Normal force increases -- and while it still mostly points in the Lift direction, it rotates back and now also points in the drag direction.
However, Lift is always perpendicular to velocity.  We define it that way.

From a practical standpoint, yes. The total aerodynamic force created by the wing is directed more aft at a high angle of attack than at a low angle of attack.
Somewhat pedantically, "lift" is defined to be perpendicular to relative wind. The part of the aerodynamic force that is increased in the aft direction is called "induced drag." This is just a matter of terminology- you are exactly correct in your intuition from a physical standpoint. This is why an airplane will slow down if pitched up without adding power- the increased drag does indeed push the plane backwards and cause its airspeed to decrease until a new equilibrium is reached at a slower airspeed.


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Turbofan engine fan blade leading edge fairing?
A lot of aircrafts feature a leading edge fairing for the wing, at the connection with fuselage, in order to reduce the airflow interference.
Aerodynamically speaking, those fan blades in the turbofan engine should also be installed with that leading edge fairing at the connection with the spinner. However I wasn't able to find one like so, not even one those recently released engines. Is this due to patent-related reasons? Does a fan blade leading edge fairing not need to be installed?

It seems that there actually are leading edge fairings featured in this case, they are just too small to be discovered, due to the thickness of these fan blades. But I'm still looking for confirmation.

Can you link a picture with the leading edge fairing of an aircraft you're speaking about?

@sophit This is what I'm looking for: https://personal.utdallas.edu/~klaus/Airplane/wing_root_fairing.html

The blade moves at a far lower airspeed at the root than it does at the tip. So only a tiny fraction of its drag comes from the root attachment.
To the extent there is a fairing, as in a smooth transition surface, it's part of the blade.


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Can pilots confirm or refute that the earth is rotating or not?
Some people claim that the plane should fly slower in one direction and faster in the other direction, if the earth is rotating.

Faster or slower relative to what? The ground? Compared to the rotation rate of the (possibly roundish) Earth?

Question text asks a very different question than the title.

@StephenS The question text contains no question at all; the only question posed is in the title. Which is clearly answerable (see below). The sentence in the body of the post is vaguely related to the title with the question in it, but the question itself is only asked in one place.

You are Zeno of Elea and I claim my £5

I would think if you justbflew due north for x period of ti.e, turned 180 and flew due aouth

Yes, I am a pilot, and I confirm that the Earth is, in fact, rotating. I know this because the sun does not remain in one stationary spot in the sky, but rather appears to move, since the planet upon which we stand is, in fact, rotating.
So yes, pilots can (and do) confirm that the Earth is rotating. That is the question that was asked, and most definitively, the answer is, yes.

It should be pointed out that you being a pilot has no bearing on your ability to confirm that the Earth is rotating. I can confirm the same thing and I am not a pilot. Also, Maupertuis confirmed the equatorial bulge (the Earth being "pulled apart" and "flattened" by its rotation) in the 1730s, several experimental physicists confirmed the Coriolis effect (objects not falling straight down) in the late 1700s and the most famous experiment, Foucault confirmed it with the pendulum experiment in 1851. None of these people were pilots.

@JörgWMittag -- re "it should be pointed out  that you being a pilot"-- why should this be pointed out?  The question asked "can pilots confirm...", and the reply said essentially "I am a pilot and I can confirm".  Sounds good to me!


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Is it possible to have a foot powered hang-glider?
My goal is to build a pedal-powered hang-glider capable of traveling at least 80 kilometers per hour. Is such a unit possible in principle, or do we need orders of magnitude more power?

Use your feet to power yourself off a high mountain top.  You can probably hit 80 on your glide down.

Sure, a glider, (in descent), but not sustained, level, flight at 80kph.

The fully fairing-enclosed recumbent bicycle is pretty much at the peak of efficiency when it comes to extracting locomotion from a human body. They have extremely low drag and are able to utilize a large percentage of the rider's muscles. The hour record (furthest distance traveled within an hour) is 92 km/h, the instantaneous absolute speed record is ~144 km/h. You are asking to achieve ~60% of the absolute top speed that an elite athlete was able to attain in the most efficient vehicle imaginable, using a vehicle that wastes a significant amount of energy just fighting gravity.

A hang glider that weighs, say, 275 lbs, with an L/D of 12, needs 23 lbs of thrust for level flight, or roughly, 4 HP.  If you want to be able to climb with a decent rate, you need more than double that, say 10 HP minimum.
A human can make just over 1 HP in a short burst, and maybe a .1 HP sustained for a minute, even less for extended periods.
So yeah, you're off by a couple orders of magnitude. It's only possible by having massively large wings, made from exotic materials to keep the massive wings light enough. For a regular hang glider, even a high end one, foggedaboudit.

80kph in level flight? No, not with current technology. Current record holder is the Musculair II with 44.26kph. See Human Powered Aircraft.

So after all, I'm talking about a hang glider, and not about aircraft with a rigid wing, and the materials are different now. But speed is not something that is obligatory for me, the main thing is to take off

I think you'll have a harder time with the hang glider than other designs, if hang gliders were much "easier", these human powered aircraft competitions would have a lot more designs like that.

@Entaldalpe Your question is contradictory. Are you asking about a foot launched glider, or a human powered aircraft? They are 2 very different things.

@MikeSowsun yes, i'm about HPA.

@Entaldalpe: "The materials are different now" – Even if you had a magic material that would allow you to reduce the weight of the vehicle to 0, that only improves your efficiency by ~30%. Even with the less advanced materials from 30 years ago, the weight of the pilot is already 2/3 of the total weight, and you cannot eliminate that weight, no matter how exotic your materials are.


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Is this the correct functioning of a reed type sensor in a stall warning system?
I understand that this type of system works based on suction. According to what I read, at angles close to the critical angle of attack, the pressure near the leading edge is very low, this generates a greater pressure differential causing an increase in lift, this low pressure generates a suction in the stall warning system, causing the reed inside the horn to vibrate and generate a sound in the cabin, however, where the air is sucked from, is it sucked from the cabin? I feel that it makes no sense for the air to first enter through the horn and then leave again but this time with sound.

Sound can travel "upwind" in this case.  Air flow is indicated in red.

the airflow for the vibrating reed is sourced from inside the cabin. As long as there is enough mass airflow to set the reed into resonance, it will "bleat" audibly. All you need to do then is select the exact port location on the leading edge of the wing to start the bleat when the critical AoA is approached. Clever and foolproof- and the only moving part is the reed!


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As of June 2019, can a DPE in the United States renew a CFI's certificate based on completion of a FIRC?
Flight instructors need to renew their CFI certificates every 24 months. One of the ways to do that is by completing a FIRC. In the past, you had to take your completed FIRC to the local FSDO and have an inspector approve it.
Lately, I've heard rumors that FSDOs are so overworked that they're not doing CFI renewals any more, and are sending them to DPEs instead.
Is this rumor true? Can I take a completed FIRC to a DPE in June 2019 and re-up my certificate?

I did the on-line eFIRC with ASI, and at the end they handled all of the renewal paperwork. No visit to a FSDO or DPE required. Path of least resistance.

Yes they can
I asked a DPE to renew mine a couple days ago and they did.  Sometimes asking nicely is the best way to learn.